Three dimensional package and architecture for high performance computer

ABSTRACT

A three dimensional packaging architecture for ultimate high performance computers and methods for fabricating thereof are described. The package allows very dense packaging of multiple integrated circuit chips for minimum communication distances and maximum clock speeds of the computer. The packaging structure is formed from a plurality of subassemblies. Each subassembly is formed from a substrate which has on at least one side thereof at least one integrated circuit device. Between adjacent subassemblies there is disposed a second substrate. There are electrical interconnection members to electrically interconnect contact locations on the subassembly to contact locations on the second substrate. The electrical interconnection members can be solder mounds, wire bonds and the like. The first substrate provides electrical signal intercommunication between the electronic devices and each subassembly. The second substrate provides ground and power distribution to the plurality of subassemblies. Optionally, the outer surfaces of the structure that can be disposed a cube of memory chips.

FIELD OF THE INVENTION

The present invention relates to a package and architecture which allowsvery dense packaging of multiple integrated circuit chips for minimumcommunication distances and maximum clock speeds.

BACKGROUND OF THE INVENTION

To reduce the cost and increase the performance or electronic computers,it is desirable to place as many electronic circuits in as small aregion as possible in order to reduce the distance over which electricalsignals must travel from one circuit to another. This can be achieved byfabricating, on a given area of a semiconductor chip, as many electroniccircuits as feasible within a given fabrication technology. These densechips are generally disposed on the surface of a substrate in a side byside arrangement with space left therebetween to provide regions forelectrical conductors for electrical interconnection of the chips. Thechip contact locations can be electrically interconnected to substratecontact locations by means of wires bonded in between the chip contactlocation and substrate contact locations. Alternatively, a TAB tape(which is a flexible dielectric layer having a plurality of conductorsdisposed thereon) can be used for this electrical interconnection.Alternatively, the semiconductor chips may be mounted in a flip-chipconfiguration wherein an array of contact locations on the semiconductorchip is aligned with and electrically interconnected to an array ofcontact locations on a substrate by means of solder mounds disposedbetween corresponding chips and substrate contact locations. This sideby side arrangement of electronic devices is not the most denseconfiguration which can be achieved.

In the microelectronics industry, integrated circuits, such assemiconductor chips, are mounted onto packaging substrates to formmodules. In high performance computer applications, the modules containa plurality of integrated circuits. A plurality of modules are mountedonto a second level of packages such as a printed circuit board or card.The cards are inserted into a frame to form a computer.

For nearly all conventional interconnection package, except for doublesided cards, signals from one chip on the package travel in a twodimensional wiring net to the edge of the package, then travel acrossthe card or board or even travel along cables before they reach the nextpackage which contain the destination integrated circuit chip.Therefore, signals must travel off of one module onto wiring on a boardor onto wiring on a cable to a second module and from a second module tothe destination integrated circuit chip in the second module. Thisresults in a long package time delay and increases the demands onwireability of the two dimensional wiring arrays.

As the performance requirements of a mainframe computer continue toincrease, the signal propagation time for communications from module tomodule, chip to chip and even device to device become critical. Thecurrent solution to this problem is to place the chips as close togetheras possible on a planar substrate and combine as many circuits aspossible onto the substrate using insulators having dielectric constantsas low as possible between wiring layers.

However, it is becoming apparent that such solutions will not allowfuture generation machines to reach the desired performance levels. Oneof the most significant factors is the time required for a signal tocross the length of a module. Three dimensional packaging structureswill overcome the problem of the signal propagation distances in theplanar packages, but the difficulty has been finding a suitable way tointerconnect the devices in such a structure.

An improvement in chip interconnection propagation time and an increasein real chip packaging density can be achieved if three dimensionalwiring between closely spaced planes of chips can be achieved.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improvedpackaging structure wherein the integrated circuit devices are packagedin a three dimensional structure.

It is another object of the present invention to provide such animproved packaging structure with both horizontal electricalinterconnections and vertical electrical interconnections.

It is a further object of the present invention to provide an improvedpackaging structure which is composed of a plurality of subassemblieseach of which are separately testable and electrically interconnected byvertical electrical interconnections.

It is yet another object of the present invention to provide an improvedpackaging structure for providing electrical interconnection to high I/Ocount chips and providing a means for dissipating heat generated in thechips.

A broad aspect of the present invention is an integrated circuitpackaging structure formed from a plurality of subassemblies. Eachsubassembly has a first substrate having a first side and a second side.There is at least one electronic device disposed on the first side andon the second side. There are a plurality of second substrates. Thesubassemblies are disposed between the second substrates. Thesubassemblies are in electrical communication with the secondsubstrates.

In a more particular aspect of the present invention, the firstsubstrates have electrical conductors for providing electricalinterconnection between the first and second sides of the firstsubstrate.

In another more particular aspect of the present invention, theelectrical conductors of the first substrate predominately providesignal I/O to the electronic devices.

In another more particular aspect of the present invention, the secondsubstrates predominately provide power distribution to thesubassemblies.

In another more particular aspect of the present invention, the firstsubstrates have a plurality of contact locations and the secondsubstrates have a plurality of contact locations. Each of the firstplurality of contact locations is disposed adjacent one of the secondplurality of contact locations. There is an electrical interconnectionmeans between the adjacent contact locations for providing electricalcommunication between the first substrates and second substrates.

In another more particular aspect of the present invention, each of thesecond substrates has an end which is disposed in electricalcommunication with a third substrate.

In another more particular aspect of the present invention, the firstplurality of electronic devices and the second plurality of electronicdevices are logic devices.

In another more particular aspect of the present invention, a stack ofintegrated circuit memory devices are disposed in contact with at leastone of the second substrates.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features and advantages of the presentinvention will become apparent upon consideration of the followingdetailed description of the invention when read in conjunction with thedrawing figures in which:

FIG. 1 is a side view of the structure according to the presentinvention.

FIG. 2 is a perspective view of the structure of FIG. 1.

FIG. 3.1 is a top view of a subassembly of the structure of FIGS. 1 and2 wherein solder mound bonding is used.

FIG. 3.2 is a top view of another subassembly of the structure of FIGS.1 and 2 wherein wire bonding is used.

FIGS. 4-9 show a method of fabricating the subassemblies of thestructure of FIG. 1.

FIGS. 10-14 shows another method for fabricating the subassemblies forthe structure of FIG. 1.

FIGS. 15-22 show the method of fabricating a metal core card for use inthe structure of FIGS. 1 and 2.

DETAILED DESCRIPTION

Referring to FIG. 1, there is shown a side view of the structure of thepresent invention. FIG. 2 shows a perspective view of the structureshown in FIG. 1. FIGS. 1 and 2 show a module 2 which is mounted onto anelectronic substrate 4, such as a printed circuit board. Module 2comprises at least one subassembly 6 or 7. The subassembly 6 comprises asubstrate 8 such as a printed circuit board, a circuitized ceramicpackaging substrate, a circuitized glass ceramic packaging structure, acircuitized polymeric packaging substrate, a circuitized metal packagingsubstrate, a circuitized glass packaging substrate a circuitizedsemiconductor substrate and the like. Substrate 8 has a first side 10and a second side 12 on each of which there is preferably disposed anelectronic device 14 and 16 respectively. The electronic devices 14 and16 are typically an integrated circuit chip. There can be a plurality ofdevices 14 and 16 on sides 10 and 12, respectively. Between thesubassemblies 6 there is disposed a second substrate 18. Substrate 18can be a circuitized ceramic, glass ceramic, glass, polymer, metal orsemiconductor substrate or a printed circuit board or a combinationthereof. On both ends of the structure of FIG. 2 there are substrates 20and 22. Substrates 20 and 22 are similar to substrate 18. Each substrate8 has a first side 24 and a second side 26. On side 24 there are aplurality of electrical contact pads 28 and on side 26 there are aplurality of electrical contact pads 30. On substrate 18, which isdisposed between subassemblies 6 and 7, there are contact pads 32 onside 34 of substrate 18 and contact pads 36 on side 38 of substrate 18.Contact pads 36 are aligned with contact pads 28 on subassembly 7.Between contact pads 36 and 28 there is disposed an electricalinterconnection means 29 which is preferably a solder mound which issoldered to pads 36 and 28. On surface 40 of substrate 20 there are aplurality of contact pads 50. Surface 46 faces surface 44 of subassembly6. On surface 44 there are pads 48 which are aligned with and adjacentto pads 50 on surface 46 of substrate 20. Between pads 48 and 50 thereis disposed electrical interconnection means 52 which is preferably asolder mound soldered between pads 48 and 50. Ends 54, 56 and 58 ofsubstrates 22, 18 and 20, respectively, are disposed adjacent surface 60of substrate 4. Electrical conductors in substrates 18, 20 and 22 extendto ends 56, 58 and 54, respectively, to provide electricalinterconnection to electrical conductors in substrate 4. The electricalinterconnection means 87 electrically connecting ends 54, 56 and 58 tosubstrate 4 can be a commonly used plug and socket or electricallyconducting pads on ends 54, 56 and 58 can be solder bonded to acorresponding set of pads on surface 60 of substrate 4 (as described inU.S. patent application Ser. No. 07/760,038, filed Sep. 3, 1991, theteaching of which is incorporated herein by reference) or any commonlyused electrical interconnection means of one substrate to another can beused. Optionally, on one of the outer surfaces 62 or 64 of thecombination structure 2 of FIG. 2 there can be disposed an integratedcircuit device. In FIG. 2 there is shown a stack 66 of integratedcircuit devices 68 which have an adhesive material 70 disposed betweenadjacent integrated circuit devices 68 in the stack to hold it together.U.S. patent application Ser. No. 07/760,038, filed Sep. 13, 1991,assigned to the assignee of the present invention, the teaching of whichis incorporated herein by reference and U.S. patent application Ser. No.07/903,838, filed Jun. 24, 1992, assigned to the assignee of the presentinvention, the teaching of which is incorporated herein by reference,teach stacked chip structures which are useful to practice the presentinvention. In the preferred embodiment from stack 66 there extends aplurality of electrically conducting wires 72 which are electricallyinterconnected to pads 74 on surface 62 of substrate 20. Electronicdevices 16 and 14 are preferably logic integrated circuit devices andchip stack 66 is preferably a stack of integrated circuit memorydevices. Although only one integrated circuit device 14 and 16 is showndisposed on surfaces 10 and 12 respectively of substrate 8, there can bea plurality of such integrated circuit devices disposed on thesesurfaces. The electrical conductors within substrate 8 providecommunication of electrical signals to the integrated circuit devices 14and 16. These signals go through pads 28 through solder mounds 52 topads 36, through electrical conductors in substrates 18, 20 or 22,through electrical interconnection means 80, 84 or 86 to electricalconductors on substrate 4. The electrical conductors on substrate 18, 20and 22 also provide for power and ground distribution from substrate 4to integrated circuit devices 14 and 16 on subassemblies 6 and 7.

In FIGS. 1 and 2, electronic device 14 can have pads 31 on surface 33 ofdevice 14. Pad 31 can be bonded by wires 35 to pads 37 on surface 10 ofsubstrate 8. Pad 57 can be in electrical connection with pads 28 throughelectrical conductors in substrate 8. Electronic device 16 can have pad41 on surface 43 of device 16. Pad 41 can be bonded by wire 45 to pad 47on surface 12 of substrate 8. Alternatively, as shown with respect todevice 14' pad 31' on the surface 32' of the electronic device can bebonded by solder mound 35' to pad 37' on surface 10' of substrate 6.Electronic device 16' can have pad 41' on surface 43' of device 16'. Pad41' can be bonded by solder mound 45' to pad 47' on surface 12' ofsubstrate 6. Alternatively, electronic devices 14, 16, 14' and 16' canbe bonded in a flip-chip-configuration with solder mounds electricallyconnected pads on the device surface to pads on the surfaces ofsubstrates 6 and 8.

FIG. 3.1 is a top view of substrate 6 showing integrated circuit device16' surrounded by contact pads 48 on which are disposed solder mounds 52and vias 80 which provide electrical connection between surfaces 12' and10' which are on the opposite side of substrate 6 or between electricalconductors on surface 12' or surface 10' to electrical conductors withinsubstrate 6. Optional solder mounds 45' are also shown with provideelectrical connection from integrated device 16' to substrate 20' FIG.3.2 shows a top view of substrate 7.

Substrate 8 of subassemblies 6 and 7 is preferably a silicon waferhaving electronic devices fabricated on opposite sides thereof.

FIGS. 4-9 show a process of fabricating a double sided silicon wafer byprocessing one side of the silicon wafer to form the integrated circuitdevice thereon and processing another in the same manner and laminatingthe two together. FIGS. 10-14 show an alternate method of fabricatingstructure 8 by the epitaxial growth of semiconductor material on asubstrate with subsequent lamination onto a pretested power signaldistribution substrate.

The structure of the present invention consists of preferably four ormore levels of devices, with capacity for through vias. Between twodouble sided devices 6 and 7 there is a substrate 18 having on surfaces34 and 36 a thin film distribution layer 18 which reroutes theinterconnections from one side 34 of the package to the other side 36 ofthe package. This substrate 18 and additionally the optional substrates20 and 22 on the outsides of the package carry both power to theelectronic devices 16 and 14 I/O of the package. The preferred methodsof how to manufacture double sided devices 6 and 7, will now bedescribed.

FIGS. 4-9 show one method of forming subassembly 6 or 7 of FIG. 1 or 2.FIG. 4 shows silicon wafer 100. On silicon wafer 100 there is disposed amultilevel semiconductor substrate 102 having devices, such as,transistors, resistors, capacitors and metallization layers as commonlyused to fabricate semiconductor devices. Contact pads 104 are depositedonto semiconductor structure 102. Solder mounds 106 commonly referred toa C4 solder balls, are disposed onto contact pads 104 by evaporationthrough metal masks or plate up as is common in the art. Alternatively,instead of using C4 balls surface mount structures can be fabricated asrepresented by regions 108 of FIG. 7 which shows a land grid array.Surface 110 of wafer 104 which is opposite to the surface on whichactive device layer 102 is disposed is ground down or etched.

The silicon wafers can be ground to medium thickness's by conventionalchem-etch processing, as known in the art. The limitation on the finalthickness of the wafer is the aspect of the through vias which can beformed in subsequent operations. For loose or current ground rulerequirements, thin wafers can be obtained by first doping the siliconwith boron. This provides a very uniform depth of boron atoms, whichprovides substantially greater solubility of the doped silicon comparedwith undoped silicon. This method provides minimal mechanical stress onthe thinned wafer, thus preventing breakage and increasing the yield ofproduct. Either of these processes can be performed at the wafer levelor chip level.

Subsequently, electrically conducting vias 102 as shown in FIG. 8 atsurface 114 are formed by selective doping. Surface 114 is disposed ontosurface 116 of substrate 118. Substrate 118 is preferably a metal core,the fabrication of which is shown in FIGS. 15-22 described below. Onside 120 of substrate 118 there is disposed another structure such asthe structure of FIG. 8 to form a double sided structure 6 as shown inFIGS. 1 and 2. The substrate 118 acts as an expansion matched power buswhile also providing thermal management and isolated signal throughholes. The core is prepatterned with a via grid matching that of theelectrically conducting vias 112.

In FIGS. 10-14 a metal substrate 200, such as a molybdenum substrate hasa plurality of electrically conducting through vias 202 formed thereinsurrounding the interior sidewall of through via 102 there is adielectric material 204 such as a polyimide. As shown in FIG. 11, alayer of semiconducting material 206 such as silicon is grown byepitaxial methods known in the art onto surface 208 of substrate 200. Asin conventional integrated circuit chips, electronic devices such astransistors, diodes, resistors and capacitors are fabricated in thesemiconducting material layer 206. As shown in FIG. 12, metallizationlayers 208 are fabricated on semiconducting structure 206. Metallization208 can be a multilevel dielectric/electrical conductor substrate as iscommonly used in the integrated circuit art, such as multilayer silicondioxide/electrical conductor structures and multilayer polyimideelectrical/conductor structures. As shown in FIG. 13, electricallyconducting pads 210 are fabricated on surface 212 of multilayerstructure 208. On pads 210 there are disposed solder mounds 214 or C4s.Two structures 216 as shown in FIG. 3 are disposed so that sides 218,which are opposite the side on which pads 210 are disposed, are placedadjacent each other with an adhesive layer 220 as shown in FIG. 14 therebetween to form structure 222 of FIG. 14 which is a double sidedelectronic device. Structure 222 of FIG. 14 can be used as subassembly 6or 7 of FIGS. 1 and 2.

The metal cores, 118 in FIG. 9 and 220 in FIG. 14 can additionally actas multichip modules as an alternative to ceramic or silicon basedmodules. It can also act as part of a laminated power supply, in whichthe metal core acts as the primary means for distributing the power andlimiting current and voltage drops due to resistance of the carrier anda thin film structure of circuit board structure laminated to this coreprovides the primary paths for signals to connect the electronic devicesto each other and to external connections.

This carrier can be fabricated as shown in FIGS. 15-22. FIG. 15 shows ametal sheet 300, preferably molybdenum, with substantially planarsurfaces. Holes 302 and 303 are produced in 300 using drill, if theground rules permit it, such as for applications as multichip modulesand laminated power supplies. When fine holes are required, patternedelectroetching is the preferred method. Holes 302 and 303 are differentsizes, depending on whether an insulated through via is to pass throughat that position or a connected via. These holes are subsequently filledusing a highly efficient filling polymer dielectric, 304, preferably athermosetting type, such as an epoxy resin, cyanate ester resin, etc,which has the thermal properties suitable for the final application, toform structure 306. Furthermore, a dielectric such as polyimide or epoxycan be conformally coated using electrophoretic, electrodeposition,powder or spray coating.

A plurality of structures similar to 306 are stacked and laminated withalternating layers of a partially cured polymer dielectric, 308 and 310in FIG. 18, which will ultimately act as an insulator to preventelectrical connection between the adjacent layers of metal. Thesepolymer dielectric layers are preferably, but not necessarily the samecomposition as the dielectric 304 used to fill the holes in FIG. 17.Inorganic materials, such as ceramic green sheet can also be utilized as308. The structures 306 are aligned as necessary to provide power andground layers for the final structure. Holes are drilled in thestructure to provide paths for electrical signals to pass, in some casesinsulated from the metal layer being passed or in electrical contact.

Alternatively, holes can be formed in the polymer filler, 304, inpositions which will ultimately be the positions for electricallyconnected vias. This can be accomplished by another drilling operationor through dry or wet etching as is commonly performed in the art.Similarly, holes are formed in in the interlayer dielectric material,308 and 310 and the layers aligned, stacked and laminated similarly tothat shown in FIG. 18. Alternatively, the holes in 308 and 310 are notformed until after lamination, using hole already formed in structure306 as the mask. This eases alignment requirements.

The laminated structure 312 in FIG. 20 is then exposed to a solutionwhich preferentially etches the dielectric in a uniform manner to ensurethat good electrical contact with the internal metal features can beobtained, to produce structure 314 in FIG. 21. The metal features areoptionally etched to produce structure 316 in FIG. 22, which is suitablefor plating of the through holes. This can be performed utilizingelectroless processes known in the art, following the formation of aseed layer. Without the final metal etching, voids in the final platedthrough holes can be formed, which will impact reliability of thestructure.

The final metal core structure can be used as a circuit board for directmounting of chips or thin film redistribution layer. It can alsofunction as a laminated power distribution structure and heat sinkdevice for thermal management.

In summary, a three dimensional packaging architecture for an ultimatehigh performance computer has been described which allows the very densepackaging of multiple integrated circuit chips for minimum communicationdistances there between and maximum clock speeds. The structure iscomprised of a plurality of subassemblies, each subassembly having atleast one integrated circuit structure on both sides of a substratewhich provides signal wiring between the integrated circuit deviceswithin the substrate. Between adjacent subassemblies there is disposed asecond substrate which provides power and ground distribution to thestructure.

What is claimed is:
 1. A structure comprising:a plurality ofsubassemblies; each of said subassemblies comprising:a first substratehaving a first side and a second side; at least one electronic devicedisposed on said first side and said second side; a plurality of firstcontact locations on said first side; a plurality of second contactlocations on said second side; a plurality of second substrates; each ofsaid subassemblies is disposed between a first one of said plurality ofsecond substrates and a second one of said plurality of secondsubstrates; first means for electrically interconnecting said pluralityof first contact locations to said first one of said plurality of secondsubstrates; second means for electrically interconnecting said pluralityof second contact locations to said second one of said plurality ofsecond substrates.
 2. A structure according to claim 1, wherein saidfirst means and said second means are selected from the group consistingof solder mounds and wire bonds.
 3. A structure according to claim 1,wherein there are a plurality of electronic devices on said first sideand a plurality of electronic devices on said second side.
 4. Astructure according to claim 1, wherein said electronic device is asemiconductor device selected from the group consisting of a siliconintegrated circuit chip and a gallium arsenide integrated circuit chip.5. A structure according to claim 1, wherein said first substrate haselectrical conductors for electrically interconnecting said electronicdevices.
 6. A structure according to claim 1, wherein said secondsubstrate has electrical conductors for providing power and ground tosaid subassemblies.
 7. A structure according to claim 1, furtherincluding a third substrate, each of said second substrates has an edgehaving electrical conductors at said edge, said edge is disposed inelectrical communication with electrical conductors on said thirdsubstrate.
 8. A structure according to claim 7, wherein said electricalconductors at said edge are electrically conducting pins.
 9. A structureaccording to claim 7, further including a stack of memory devices inelectrical communication with one of said second substrates.
 10. Astructure according to claim 9, further including at least one memorydevice disposed in electrical contact with said second substrate.
 11. Astructure according to claim 1, further including means for directlyelectrically interconnecting said at least one electronic device to atleast one of said plurality of second substrates.
 12. A structureaccording to claim 11, wherein said means for directly electricallyinterconnecting said at least one electronic device to said at least oneof said plurality of second substrates is a solder mound.
 13. Astructure comprising:a plurality of subassemblies; each of saidsubassemblies comprises a first substrate having a first side and asecond side, a first at least one logic electronic device being disposedon said first side, a second at least one electronic devices beingdisposed on said second side, said first substrate has electricalconductors for electrical interconnection to said first and said second,said first substrate has a plurality of first contact locations; aplurality of second substrates, each having an end; said subassembliesare disposed between said second substrates; said second substrates havea plurality of second contact locations; said first contact locationsare disposed adjacent said second contact locations; a means forproviding electrical interconnection between said second substrates andsaid first substrates; a third substrate; said ends of said secondsubstrates being disposed adjacent said third substrates; means forproviding electrical interconnection of electrical conductors at saidends with electrical conductors in said third substrate.